This invention relates to rotary torque transmitting devices in general and is particularly directed to an improved damper arrangement for these devices.
In conventional passenger cars and trucks, objectionable driveline vibrations may occur at certain speeds and load conditions. Some of these disturbances may be eliminated or reduced to an acceptable level with the incorporation of a torsional damper in the driven disc portion of the vehicle clutch. Damping is normally provided by a plurality of circumferentially spaced coiled springs operatively connected between relatively rotatable elements of the clutch driven disc assembly.
Clutches with dampers are widely used in all types of power transmissions systems. In certain applications, it has been found advantageous to have a damper arrangement which permits varying rates of deflection between the rotary elements. The purpose of this type of arrangement is to have a damper function in a first torsional range to produce a low deflection rate for overcoming minor vibrations, chatter and the like, and in a succeeding torsional range to produce a high deflection rate for accommodating peak shock loads and for high torque load transmission.
Known devices have achieved two-stage damping by providing heavy and light springs which act in series and by coaxially arranging springs which operate in parallel. In the first instance, it is necessary to reconstruct the spring openings of conventional rotary elements to accommodate the added length of a second spring or to reduce the axial length of both springs in order to fit conventional openings.
To function properly, the latter coaxial spring design has required either considerable structural modifications in the mating spring openings of the relatively rotatable elements or, when conventional openings are used, springs of differing lengths. Neither is entirely satisfactory from a structural or cost standpoint.
Thus, while the two-stage concept is not new, the known methods used to accomplish the desired results are not acceptable in heavy duty applications for one reason or another.
It is an object of the present invention to provide a clutch driven disc with an improved two-stage coaxial damper spring arrangement which is simple in design and will not require any additional space to accomplish the desired result.